ALBERT

Description: Advancements in the Global Geodetic Observing System (GGOS) have enabled us to investigate the effects of lateral heterogeneities in the internal Earth structure on long-term surface deformations caused by the Glacial Isostatic Adjustment (GIA). Many theories have been developed so far to consider such effects based on analytical and numerical approaches, and 3D viscosity distributions have been inferred. On the other hand, fewer studies have been conducted to assess the effects of lateral heterogeneities on short-term, elastic deformations excited by surface fluids, with 1D laterally homogeneous theories being frequently used. In this paper, we show that a spectral finite-element method is applicable to calculate the elastic deformation of an axisymmetric spherical Earth. We demonstrate the effects of laterally heterogeneous moduli with horizontal scales of several hundred kilometers in the upper mantle on the vertical response to a relatively large-scale surface load. We found that errors due to adopting a 1D Green’s function based on a local structure could amount to 2–3% when estimating the displacement outside the heterogeneity. Moreover, we confirmed that the mode coupling between higher-degree spherical harmonics needs to be considered for simulating smaller-scale heterogeneities, which agreed with results of previous studies.

Description: As a supplement to Huang et al. (2021) “Anelasticity and lateral heterogeneities in Earth’s upper mantle: impact on surface displacements, self-attraction and loading and ocean tide dynamics”, the global amplitude and root-mean-square fields of surface vertical displacement and self-attraction and loading due to ocean tide loading - the M2 tide derived from model TiME (Sulzbach et al., 2021), and the root-mean-square fields of M2 tide are presented here. The fields have been calculated for the 1D elastic solid Earth model PREM and 3D and 1D anelastic models. Figures 4-7, S1 and S2, and tables 1-2 in Huang et al. (2021) can be easily reproduced from these data fields applying the calculus discussed in the paper. The anelastic Earth models can be constructed with the methodology outlined in Huang et al. (2021) by making use of the elastic and attenuation tomography models from the University of California, Berkeley (Karaoğlu, H. & Romanowicz, B., 2018) and the École Normale Supérieure (ENS) de Lyon (Debayle et al., 2020), respectively. All response fields (U and SAL) are calculated with the spectral-finite element method (Martinec 2000, Tanaka et al. 2019).

Description: As a supplement to Huang et al. (2022) “The influence of sediments, lithosphere and upper mantle (anelastic) with lateral heterogeneity on ocean tide loading and ocean tide dynamics”, we provide for the advanced earth model LH-Lyon-3Dae [consisting of 3D elastic sediments, lithosphere and 3D anelastic upper mantle structures, see Huang et al.(2022) for details] the solutions of vertical ocean tide loading (OTL) displacement, self-attraction and loading (SAL) elevation, and ocean tides. Solutions for three tidal constituents, i.e., M2, K1 and Mf, are given. As a comparison, solutions based on the 1D elastic model PREM and the 1D anelastic LH-Lyon-1Dae are also presented. With these solutions, the primary results in Huang et al. (2022) such as the model amplitude differences, RMS differences and the predictions in GNSS stations can be reconstructed.

Description: The recent global MHD simulation code (REPPU code by Tanaka [2015]) successfully reproduces even observed phenomena such as the auroral breakup of the substorm. We judge that the simulation code correctly reproduces the physical processes of the magnetosphere and ionosphere from the fact that the phenomenon is reproduced realistically. REPPU code employs several empirical parameters expressing the non-MHD mechanisms. We tried to determine the optimal values of the parameters by using the data assimilation technique. For this purpose, we improve the REPPU code to include both the effect of the inclined rotation axis of the Earth and the effect of the discrepancy between the rotational axis and the magnetic axis. Next, we apply the data assimilation technique to determine the ionospheric conductivity distribution which is given as empirical parameters in the original REPPU code. For this purpose, we use the ionospheric electric potential determined by SuperDARN and AE indices. We employed the ensemble variational method as the assimilation technique to obtain the optimal values of the parameters. As a result, we obtained that the ionospheric conductivities are enhanced compared with the empirical results. At the same time, modification of the ionospheric conductivity does not change significantly the magnetosphere. The simulation data become the “reanalysis data” of the space weather which is useful for space weather research. Our future goal is to provide a database of the reanalysis data for space weather.

Description: Geodetic observations such as GNSS and InSAR have detected posteruptive crustal deformations. Those deformations are generally interpreted by a combination of several geophysical processes. One of such processes is viscoelastic relaxation of the lower crust and mantle, which occurs on time scale of years. The stress change within the viscoelastic layer which is caused by the coeruptive (i.e., elastic) deformation continues to relax until a new equilibrium is attained. The new equilibrium reflects the effects of self-gravitation of the Earth. In other words, a new isostatic state is realized when the stress dissipation is completed. This mechanism is common with glacial isostatic adjustment (GIA) and postseismic relaxation. In modeling posteruptive deformations, however, the effects of self-gravitation have often been neglected. In previous work, we developed a spectral finite element approach that accounts for self-gravitation and applied it to the GIA and postseismic relaxation. In this study, we apply the same approach to posteruptive deformation and theoretically evaluate the effects of self-gravitation. We derive a weak formulation associated with the source condition of horizontal and vertical opening. The validity of the formulation is verified with comparison with an analytic solution for the coeruptive deformation. Preliminary computational results show that the self-gravitation reduces the longer-wavelength deformation, which is consistent with the case of postsesmic deformation. In the presence of gravity, the long-term height of caldera could decrease in order to achieve isostacy, compared with the case excluding it.

Description: The power spectral densities of the micro-barometric, geomagnetic, and GPS-TEC fluctuations at the Phimai station in Thailand showed the sharp peaks of power spectral densities at around 220 and 270 seconds after the passage of the Lamb waves generated in association with the Hunga-Tonga submarine volcanic eruption on January 15, 2022 and orbited the Earth. The sharp spectral peaks were presumed to be caused by a vertical acoustic resonance. Lamb waves are basically sound waves that propagate horizontally in the lower atmosphere, but vertical acoustic resonance is a phenomenon caused by sound waves that propagate in the vertical direction. In this report, we also show the vertical resonance phenomena observed at other stations. The relation with a global amplitude enhancement of magnetic ripples observed by the Swarm satellites is discussed.

Description: To promote interdisciplinary studies of solar-terrestrial physics with different types of observation data, the Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project started in 2009, participating in five institutes (Tohoku University, National Institute of Polar Research, Nagoya University, Kyoto University, and Kyushu University). In this project, we have added data information (metadata) for various kinds of ground-based observation data in the solar-terrestrial physics and built a practical database (IUGONET Type-A) to share them on the Internet. We have also developed an integrated data analysis tool (IUGONET Data Analysis Software: UDAS) written in an Interactive Data Language (IDL). This analysis tool is a plugin software for Space Physics Environment Data Analysis Software (SPEDAS) to analyze and visualize various kinds of observation data. In the IUGONET Type-A, users can easily learn characteristics of observation data through the quick look images/plots and how to use several basic commands to visualize the data. Recently, we updated Space Physics Archive Search and Extract (SPASE) metadata schema from 2.2.6 to 2.4.0 so that we can describe a Digital Object Identifier (DOI) and Open Researcher and Contributor ID (ORCID) in the IUGONET metadata. In order to enhance an international use of these IUGONET products and to promote interdisciplinary studies of solar-terrestrial physics, we have held tutorial seminars and workshops several times in both Japan and foreign countries. Through these activities, many scientific papers and Master/Doctor theses have been published by using an analysis environment. These facts prove that the IUGONET products effectively work as an international platform.

Description: We had common technical requirements for the magnetic field measurement in the ARASE(ERG) mission to study the the Earth's radiation belt and the BepiColombo mission to study the Mercury environment. We had to build very precise magnetometers which are small, light and low power-consumption as well as being tolerant of the severe radiation in the Earth's radiation belt and around Mecury. We first investigated and developed MGF-I, one of two magnetometers for the BepiColombo MIO(MMO) satellite. For MGF-I, the tolerance to the high-temperature environment was also required. Another magnetometer, MGF, with almost the same design as MGF-I, was built and installed on the ARASE satellite. ARASE was launched in 2016 and has been continuously observing the radiation belt for six years since it started regular observations in March 2017. Thereafter, BepiColombo was launched in October 2018. It has performed one Earth flyby, two Venus flybys, and two Mercury flybys until 2022. The observations by MIO are mainly performed at flyby events until the Mercury orbit insertion in 2025. Due to the strict limitations and restrictions of the data, it is not easy to evaluate precisely the in-flight performance of MGF-I on BepiColombo MIO. We are investigating the performance of MGF-I based on our knowledge and analysis of data from ARASE MGF. We report the results and discuss the perspective of the observation by BepiColombo MIO MGF-I after the insertion to the orbit around Mercury.

Description: A series of numerical experiments are performed to revisit the physical mechanism of tide-induced "near-field mixing", which has been thought to be caused by the breaking of high- wavenumber internal tidal waves. We find that, for strong tidal currents with an excursion parameter Te (= kHU0 /ω with kH the wavenumber of the seafloor topography, U0 the amplitude of the tidal current, and ω the frequency of the tidal current) much larger than unity, it is the high-wavenumber internal lee waves excited over the seafloor topography that propagate upward while interacting with the background Garrett-Munk (GM) internal waves to induce near-field mixing. The vertical profile of the resulting mixing hotspot is classified by the steepness parameter Sp (= Nh/U0 with N the buoyancy frequency and h the amplitude of the seafloor topography). When Sp 〉 0.3, the near-inertial flow formed over the seafloor topography is enhanced by absorbing part of the energy of the internal lee waves propagating from below, while breaking the internal lee waves and inhibiting their continuous upward propagation, resulting in the formation of a "short mixing hotspot". In contrast, when Sp 〈 0.3, the near-inertial flow formed over the seafloor topography disappears, allowing the internal lee waves to continue to propagate upward while interacting with the background GM internal waves to form a "tall mixing hotspot". This tall mixing hotspot, extending from the seafloor to the main thermocline, may serve to compensate for the lack of turbulent mixing intensity to sustain the global overturning circulation.

Description: In the Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project, we have been creating metadata for ground observation data in space physics and populating them into the database since 2009 (http://www.iugonet.org/). These metadata followed the IUGONET metadata schema version 2.4.0.1, which is an extension of the SPASE (Space Physics Archive Search and Extract) metadata schema version 2.4.0.The IUGONET metadata database is very useful for researchers to search for data that they need and to obtain detailed information about data, but the metadata search is available only through the IUGONET page or NASA Heliophysics Data Portal. To promote data usage by a wider research community or the general public, it is needed to convert the metadata database from SPASE to more general schema so that the metadata can be ingested into other metadata databases. For that purpose, we developed a mapping table from SPASE to the JPCOAR (Japan Consortium for Open Access Repository) schema, which has been widely used for scholarly communication and data publication in Japan. Based on the mapping table, we converted part of our metadata, which describe data created in Nagoya University, to those in the JPCOAR schema. The converted metadata were registered in the institutional repository of Nagoya University (https://nagoya.repo.nii.ac.jp/). These metadata are consequently harvested by Institutional Repositories DataBase (https://irdb.nii.ac.jp/), Data Catalog Cross-Search System (https://search.ckan.jp/), and Google Dataset Search (https://datasetsearch.research.google.com/). We plan to do the same action for the other IUGONET metadata. This will significantly enhance findability and accessibility of the IUGONET metadata and their describing data.